Separation of rosin acids



Patented Jan. 1, 1952 ts -to- ,The Fulwa lChemical Corpo- Wale ironing."(Giesemann) n n LT1.

` `This `inventionQ relates to ,separationwof .i aidsandistconcernedwithxwosphases o s uch Separation., one, phase providgffn Sparationefmixed rosin `acids frorfifosinY materia-1s containng .otherconstituents, and thefotherphase Fprof The solution thus prepared'cntinsthe `rlii'sin "acd "-s aitseas lsoluteebut with#l the neutrals inf-anundissolyed state. The solution is then-extracted 'with ethrfandj-aftrseparation ofL the etherflayy stitgent father' than ifaetgydroabiencaciers still 'pre'sntfieven"afterithe selective separation l ofA `thehydrabi'tic aCidS'; but that the dehydroabie'tic 3 acid may even beseparated from such minor fraction.

With the foregoing general description of the process in mind, attentionis now directed to certain variables and examples.

First note that the alkali to be employed fin preparing the aqueoussolution may be any of the alkali metal hydroxides and carbonates suchas sodium hydroxide or sodium carbonate. As already indicated, thequantity of alkali present during the first phase of treatment, i. e.,the phase for separation of neutrals, should be only sufficient to reactwith the rosinracids present. This, of course, will depend upon theparticular rosin material being treated.

The presence of excess alkali at the time of the second phase of thetreatment, i. e., the fractional acidification, is of no detriment, butwould,`

of course, require the addition of moreacid in order to reduce the pHrvalue of the solution to the range in which the rosin acids may beprecipitated.

For the purpose of extracting the neutrals after initial preparation ofthe solution of the sodium salts of the rosin acids, a non-polarvsolvent should be employed, such as ether.

The concentration of the rosin acid Vsalts in the aqueous solution isnot critical. It is Vpreferred, however, to employ a dilute solutionbecause this enables greater precision in the separation of rosin acids,for instance a concentration of from a fraction of 1% up to 10% basedon, the rosin acids. A concentration of from 3% tov 5% has been found tobe particularly eiective.v

A mineral acid should be usedfor the fractional acidication of thesolution, for instance hydrochloric acid or sulfuric acid, hydrochloricacid being preferred. It is further preferred to yuse the acid in diluteform, say from 0.1 to 0.5 normal, advantageously 0.1 normal. Y l

The amount of acid added at each stage ofthe frictional acidificationwill, of course, depend upon the fractions desired to be separated andthis in turn will depend upon the proportions of the various rosin acidspresent in the mixture taken for treatment.

Efficient or thorough stirring should be used during the acid addition,sinceA the precision of separation Yof the desired rosin acid fractionsis thereby greatly enhanced. I

All operations are effective -at room temperature. There is no advantageat all in working at.' other temperatures in the rst phase of treatment.However, the second phase may well be carried out at highertemperatures, even at the boiling point, during the addition of mineralacid andin this case each addition of mineral acid should be followed bycooling to room temperature before filtration. In this way the sharpnessof the separation is enhanced by the additional factor ofcrystallization.

It is here further pointed out that the rst phase of the treatment(separation of neutrals) may be applied not only to variousdisproportionated rosins, but even to other rosin materials where aseparation of neutrals is desired.

In use of the invention for securing dehydroabietic acid in relativelypure form, any of a variety of disproportionated rosins may be selectedas starting material. Thus, the type of product resulting frompalladium-charcoal disproportionation may be used, or, if desired,dehydroabietic acid may be separated from rosin which has beendisproportionated by heating in the presence of sulfur dioxide, asdisclosed, for

4 example, in Nicholas L. Kalman Patent No. 2,378,295.

EXAMPLES Example 1.-This example illustrates the separation of neutralsfrom a disproportionated rosin.

Rosin disproportionated with palladium-charcoal was used in thisexample. The disproportionated material contained about 55%dehydroabietic acid, about 33% hydroabietic acids, and 12% neutrals.34.1 g. of this disproportionated rosin (containing g. of rosin acids,0.1 mol, and 4.1 g. neutrals) was ground in a mortar and then dissolvedvin 500 ml. of water and 205 ml. of 0.489 N, sodium hydroxide (0.1 molsodium hydroxide) heated to 95 C. The solution was agi- .tated andallowed to cool, thus yielding a turbid .solution containing 3% rosinacids in the form of their `sodium salts. This solution was then shakenwith 800 ml. of ether and allowed to stand. The clear, almost colorless,aqueous layer was removed and the ether layer evaporated to dryness,yielding 4.6 g. of light brown, viscous oil. The aqueous solution wasthen shaken with V 500 ml. of ether and separated. This time the etherextract gave 0.5 g. of a light yellow sticky solid. Vacuum and warmingremoved the ether dissolved in the aqueous solution, and completeacidification of a portion of this aqueous solution gave a whiteprecipitate of mixed rosin acids, having acid number 181.

Additional batches of g. and 175 g. of the same disproportionated rosinwere worked up with the same results.

Example 2.--Neutrals were separated from another disproportionatedrosin, as follows:

In this example a disproportionated rosin was prepared with the use ofsulfur dioxide. 179.8 g. of this rosin (150 g. rosin acids, 0.5 mol and29.8 g. neutrals) was dissolved in the same manner described in Example1 above in a solu.- tion containing 0.5 mol of sodium hydroxide andsufficientv water to make 5 liters yielding a solution containing 3% ofrosin acids in the form of theirV sodium salts. This was decanted from1.9 g. of an insoluble, viscous oil found to be present. One liter ofthe decanted solution was shaken with 800 ml. of ether and separated.The ether layer contained 4.7 g. of an oily material. This portion ofthe aqueous solution was again extracted with ether. yielding an addi'-tional 0.7 g. of oil. On complete acidiiication of a portion of theextracted solution a tine white precipitate was obtained having an acidnumber of 170.

Example 3,-The following illustrates the fractional acidification ofrosin disproportionated with palladium-charcoal and previously freedfrom neutrals in accordance with Example l above.

An aqueous solution having a total volume of 2500 m1. and containing58.75 g. of the mixed rosin acids as their sodium salts (2.35% withrespect to the acids) was subjected to fractional acidification, beingeilciently stirred throughout. The initial pH of the solution was 10.85and this was lowered. by vgradual addition of 0.103 N hydrochloricacid.v The rate of addition varied between 0.5 and 2.5 ml. per minute,depending upon the amount of precipitation produced. A fter each minuteof addition the flow of acid was stopped and the pH recorded followingthe lapse of another minute. acidication in which the first fraction wasprecipitated the pH of the solution decreased During the yai:enlace to 9and remained at this value through- 'oiit the precipitation of the firstfraction. After iiitration of this first fraction, the filtrate wasacidied-further, during which theypH sank to 8.65 'with noprecipitation. Further acid addition precipitated" another' fraction:between pH additional `fractions were manner 'a number of `folztfained,`and the `finalfraction wasv precipitated by "the *addition 'of excessacid to remove come p letely all remaining rosi'n acid nthe solution.The precipitates after filtration, were washed "free :f `chloride ionwith 'water,` dried and WEIC. n 4

The quantity of precipitate securedin each of seven fractions accordingto the foregoing, and other pertinent data' are given in Table I justbelow.

For identification purposes exactly equal amounts of each of the sevenfractions, and also of an authentic sample of pure dehydroabietic acid,were esterifed with excess dioazomethane in ether and any crystallinemethyl dehydroabietate carefully isolated for yield and purity. Theresults of these esterifications are given in Table II just below.

From the above it will be seen that fraction 5 is substantially puredehydroabietic acid and that fractions 4 and 6 are mainly composed ofthis acid. A correction Value of 4% may be added to the actualpercentages of ester obtained for these three fractions, since the yieldpercentage of ester from pure dehydroabietic acid indicates 4% loss byester solubility in the crystallizing solvent, methyl alcohol. It willbe seen therefore that, based on the amount of methyl ester isolatedfrom the three esteried. fractions, 5060% of the theoretical amount ofdehydroabietic acid in the mixed acids has been separated in a state ofpurity suii'cient for virtually any purpose.

Example 4.-'I`his example illustrates fractional acidification of mixedrosin acids by the use of hydrochloric acid and sodium carbonate.

The mixed acids taken for treatment comprised about 63% dehydroabieticacid andt37% hydroabietic acids. A batch of 30 g. of the mixed acids g.of sodium carbonate.

was dissolved in 30001111. of water "containing 10.7 rIhis formed aclear solution at room temperature and had aninitial pH of 9.3. Y

The solution was brought to a boil and 0.1 N hydrochloric acid was addeddropwisc with stirrring tbthe point :of incipient turbidityywhere- 'uponthe solution was cooled to room temperature, resulting in precipitationand crystallization of a small fraction which was ltered, washed withwater, and crystallized once from `aqueous ethanol. v i The filtrate wasagain raised to boiling `temperature and hydrochloric acid again addedin the manner described `above to secure another small fraction. This'fractionating treatment was `repeated until no more precipitate wa'ssecured,

and thereby 25 fractions were obtained.

The pH of th-e solution being fractionated was Itaken after eachfiltration, and it was Vfound that the"`f1'"act`ions precipitatedbetween a pH of 'about 8.5 Ia'ndlabout '1.5 (fractions 16 to'2l of theseries) comprised substantially puredehydroabietic acid. This was shownby combining this group of frac- 'tions and establishing theneutralization equivalent thereof, which was 298. Calculated for puredehydroabietic acidi: 298. Y Y

' A sample of the above combined fractions was 'esteri'iied withdimethyl sulfate in the usual manner, from which pure methyldehydroabietata `of melting peint ST1-652 C., was obtained'.` Amixedmelting point with authentic methyl dehydroabietate showed nodepression.

It will be understood that where it is desired to separatedehydroabietic acid, Without separation of other individuals withrespect to each other, the fractional acidication may be carried outmerely in two stages, instead of a multiplicity. When operating in thisWay, the quantity of acid added in the first stage of acidication shouldbe sufficient to bring the pH value of the solution down to about 8.5.This will effect precipitation of the bulk of the acids present otherthan dehydroabietic acid. A second addition of acid may then be made tothe solution suiicient to bring the pH down to about 7.5. This secondstage of acidification will yield a precipitate constitutingsubstantially pure dehydroabietic acid, the quantity of which will beover one-half of the total quantity of dehydroabietic acid initiallypresent in the mixed acids taken for treatment.

Such two-stage fractional acidification has been effected under thegeneral conditions fully outlined above, with results as to yield andpurity of the same order as those indicated by the tables given above.

I claim: t

1. The method of separating dehydroabietic acid from disproportionatedrosin comprising dissolving disproportionated rosin in an aqueousalkaline solution to thereby form an aqueous solution of the alkalisalts of the rosin acids present, adding mineral acid to the solution inan amount suiiicient to react with the alkali salts of the hydroabieticacids present but insufficient to react with the alkali salts ofdehydroabietic acid present, separating the resulting precipitate `ofhydroabietic acids, and thereafter recovering the dehydroabietic acidconstituent from the solution.

2. A method according to claim 1 in which the addition of mineral acidis effected in two stages, the rst of which is sulcient to reducethe pHvalue of the solution to 8.50 to thereby precipitate rosin acids otherthan dehydroabietic acid,

and the second of which is sufficient to reduce the pH value of theremaining solution to 7.50 to thereby precipitate dehydroabietic acid.

3. The method of separating dehydroabietic -acid from disproportionatedrosin comprising separating neutral constituents from such rosin,

reacting- `the rosin acids present with an alkali selected from theclass consisting of alkali hydroxiclesand alkali carbonates in aqueoussolution to `thereby form an aqueous solution of thel alkali salts ofsaid acids, adding mineral acid to the solution in an amount suiiicientto react with the alkali salts of the hydroabietic acids present butinsufficient to react with the alkali salts of dehydroabietic acidpresent, separating the resulting precipitate of hydroabietic acids.,and

thereafter recovering the dehydroabietic acid constitutent from thesolution.

4. A method according to claim 3 in which the disproportionated rosin isfirst dissolved in an i8 rosin acids from rosln materialsvcontainingsuch acids in admixture with neutral constitutents, which methodcomprises dissolving said rosin material in an aqueous alkaline solutioncontaining a quantity of an alkali selected from the group consisting ofalkali hydroxides and alkali carbonatessubstantially equal to but notgreater than that quantity required to react with the rosin acidspresent to thereby form an aqueous solution of the alkali salts of therosin acids having the neutral constituents suspended therein,extracting the solution with ether, and thereafter recovering therosinacid constituents. A

7. A method according to claim 6 in which the recovery of the rosinvacidconstitutents is effected by .fractional acidification of the solutionafter .extraction of the neutrals.

HAROLD H. zExss i REFERENCES CITED v The following references are ofrecord in the tile of this patent:

UNITED STATES PATENTS 2631-2636, November 1938.

1. THE METHOD OF SEPARATING DEHYDROABIETIC ACID FROM DISPROPORTIONATED ROSIN COMPRISING DISSOLVING DISPROPORTIONED ROSIN IN AN AQUEOUS ALKALINE SOLUTION TO THEREBY FORM AN AQUEOUS SOLUTION OF THE ALKALI SALTS OF THE ROSIN ACIDS PRESENT, ADDING MINERAL ACID TO THE SOLUTION IN AN AMOUNT SUFFICIENT TO REACT WITH THE ALKALI SALTS OF THE HYDROABIETIC ACIDS PRESENT BUT INSUFFICIENT TO REACT WITH THE ALKALI SALTS OF DEHYDROABIETIC ACID PRESENT, SEPARATING THE RESULTING PRECIPITATE OF HYDROABIETIC ACIDS, AND THEREAFTER RECOVERING THE DEHYDROABIETIC ACID CONSTITUENT FROM THE SOLUTION. 